1. Technical Field of the Invention
The present invention relates to a tool retention mechanism, for example, typically used to retain a cutting tool holder in a tool pocket of a tool changer magazine. A horizontal machine tool apparatus typically contains a plurality of tool pockets attached to a movable tool changer magazine and the mechanism of the present inventions provides an affirmative mechanism for retaining tool holders so that they do not separate from their respective tool pockets unless removal is desired. More particularly, a pair of opposed pivotal fingers each include a latch which can engage with or disengage from the internal groove of a tool holder to perform this function. A biasing force can be provided, for example, by one or more springs, to encourage this affirmative engagement of the latches with the internal groove.
2. Brief Description of the Related Art
The present invention relates to a cutting tool retention mechanism. This mechanism is designed to be received in a tool pocket and to interface with and retain within the tool pocket a tool holder having an internal groove, such as, for example, a xe2x80x9chohlschaftkegelxe2x80x9d (or xe2x80x9cHSKxe2x80x9d) tool holder. An HSK tool holder is a special form of tool holder configured according to a xe2x80x9cDINxe2x80x9d (German engineering) standard and designates short, hollow, tapered tool shanks, wherein the tool shank includes a conical surface and a face formed on an integral tool changer gripping flange thereof, and wherein a machine tool spindle is adapted to grip both the conical surface and the face of the tool holder for positive rotation thereof. Unlike well-known ANSI (American National Standards Institute) standard solid tool holders, which are pulled into a spindle seat by way of a retention stud extending from the generally cylindrical shank thereof, an HSK tool shank has an internal relief, or retaining groove, so that, once inside a machine spindle, internal gripping fingers of the spindle assembly direct outward and rearward forces against the tool shank, to retain it securely.
Low-force analogues of spindle gripping arrangements are known for retaining hollow shank tools within tool storage pockets, for example, the employment of spring loaded balls which engage the tool retaining groove. Typically, an external actuating means is employed to release the tool from its tool storage receptacle.
The present invention relates to a cutting tool retention mechanism, for example, typically used to retain a tool holder in a tool pocket of a tool changer magazine. A tool changer magazine of a horizontal machining center contains a plurality of tool pockets, each of these tool pockets being adapted to store one tool such that, by the tool changer magazine, a plurality of tools are accessible to the machining center for performing a variety of machining operations, for example, utilizing a rotating spindle. In operation, when the machining center needs to utilize any specific tool for a specific machining operation, the tool changer magazine is moved such that the desired tool in its tool pocket is positioned in an index location where the desired tool can be removed from the pocket and mounted to the spindle. Typically, a machining center will retrieve (and replace) between 5 and 25 cutting tools during a complete machining cycle of a typical workpiece. With each tool change, the entire magazine, and as such, each of the tools held in the pockets thereof, moves. Therefore, because of the frequent, and sometimes jerky, movement of the magazine, it is desirable to provide for affirmative retention of the various tool holders in their respective tool pockets until such time as a specific tool is needed is desirable, and the current invention provides for this retention.
All of the embodiments disclosed herein have similar function. In function, a fulcrum supports at least a pair of opposed fingers which function as levers. Springs are used to provide a biasing force such that the bias portions of the opposed fingers are urged toward each other to a physical limit controlled, in one embodiment hereof, by a pair of channels provided in a spring plate. The finger bias portions are on one side of the fulcrum and the finger latch portions are on an opposite side of the fulcrum, such that, in this configuration, opposed latches toward the end of the finger latch portions are spaced a furthest distance from each other. In this configuration, the latches are spaced to engage an internal groove in an HSK tool holder to retain that tool holder in its respective tool pocket.
A tool holder can be forced on and off the latches. For example, when pushing a tool holder into the receiving portion of the tool pocket body, the holder will engage the opposed latches. As these latches are spaced a distance apart greater than the smallest diameter of the holder, a force will be applied to the latches overcoming the biasing force, provided by the springs, which is applied toward the opposite end of the fingers on the other side of the fulcrum. When the holder is pushed into the receiving portion a sufficient distance for engagement of the latches with the HSK tool holder internal groove, the springs will force the latches away from each other to affirmatively hold the tool holder. Alternatively, the finger bias portions can have a force applied thereto to overcome the force of the springs to push the finger bias portions away from each other, as permitted by the geometry of the spring plate channel. The separation of the finger bias portions causes the opposed latches on the finger latch portions on the opposite side to the fulcrum to move toward each other. This action can be initiated for insertion or removal of a tool holder and would cause less parts xe2x80x9cwear and tearxe2x80x9d, but requires additional components to implement.
The preferred embodiment of the present invention employs a unitary tool retention mechanism constructed of plastic. In another embodiment, a unitary plastic tool retention mechanism employs a wear-resistant surface in the form of, in one embodiment hereon, shields attached to the finger latch portions. The shields can be of metal or other material with high wear resistance to prolong the life of the mechanism. Alternatively, the mechanism, itself, can be constructed of a wear-resistant material, in which case, the shields are unnecessary. In yet another embodiment, a plurality of components are employed to permit the fingers to be made of a wear-resistant metallic material, such as steel, with the inclusion of the lever pivot by insertion of pins through bores in a retention support and each finger.
In still another embodiment hereof, a plurality of pairs of opposed fingers, or an odd number of individual fingers, are spaced equidistantly around the support. In an even further embodiment hereof, the pair of opposed fingers is replaced with a single finger, in which case, the latch distance and the bias distance are defined as the distance of the latch and the bias portion, respectively, to a reference, such as, for example, the central axis of the support.
More particularly, in the preferred embodiment hereof, the present invention comprises a retention mechanism having a pair of opposed fingers, each of the fingers extending from a support, each of the fingers having a latch spaced from the support, the support permitting each of the fingers to be pivoted to vary a latch distance between the latches.
Further, where each of the fingers has a latch portion including the latch and a bias portion, and where, when at least one of the fingers is pivoted to vary the latch distance, a bias distance between the bias portions varies oppositely thereto, as permitted by the support. That is, where at least one of the fingers is pivoted to decrease the latch distance, the bias distance will increase, although not necessarily inversely thereto. Additionally, each bias portion may have a spring to exert a biasing force on the bias portion, thereby urging the bias portion in a direction toward the bias portion of the other finger.
As the retention mechanism is designed to permit the latches to engage an internal groove of a tool holder, the latches preferably have an orientation away from each other, although the latches may have any configuration suitable to engage the internal groove of the tool holder.
These and additional objects, features and advantages of the present invention will become apparent to those reasonably skilled in the art from the description which follows, and may be realized by means of the instrumentalities and combinations particularly pointed out therein.